Electronic equipment (such as, for example, television sets and other audio/video equipments) are commonly implemented using digital technology instead of analog technology. Typically, the more advanced the digital technology gets the more demanding the task of converting an analog signal to a digital signal suitable for the digital technology implementation becomes.
Conceptually, an analog-to-digital converter (also denoted ADC or A/D converter) is very well know in the art as well as its basic functionality (sample-and-hold, quantization) and will not be elaborated on further herein.
For high sampling frequencies it may be necessary or at least beneficial to use ADC structures comprising several constituent ADC:s to be able to accommodate the high sampling frequency. Such structures alleviate the processing speed requirements on each constituent ADC. Examples of such ADC structures are pipe-lined ADC:s and time-interleaved ADC:s (e.g. parallel successive ADC:s). US 2011/0304489 A1, WO 2007/093478 A1, EP 0624289 B1 and WO 2010/042051 A1 describe various example time-interleaved ADC structures.
All electronic equipment has inherent imperfections, which may be more or less prominent. This is, of course, also the case for ADC:s, and in particular for each constituent ADC of a time-interleaved ADC. It may be desirable to estimate the imperfections to be able to compensate for them. For example, compensation may be applied in the digital domain, in the analog domain, or both in the digital and analog domain.
A drawback of the known techniques for imperfection estimation is that they cannot be performed during the conversion of any analog signal. It is required to either have a separate estimation session (e.g. in connection to the production of the ADC) or to rely on a known signal part being incorporated in the analog signal (see e.g. US 2011/0304489 A1 where estimation of offset errors rely on a known signal level which is repeatedly present in the analog signal). Thus, if an analog signal with no known signal part is to be converted and there are imperfections that change dynamically over time, it would be cumbersome to provide compensation for those imperfections.
Therefore, there is a need for alternative and improved methods and arrangements for estimation of imperfections of a time-interleaved analog-to-digital converter.